There have been active studies on estimation of human posture based on image data from a captured moving picture. A posture estimation apparatus can determine a person's motions from a moving picture through computer analysis and thus can perform behavior analysis without involving manual works. Applications of behavior analysis include detection of abnormal actions on the street, analysis of in-store purchase behaviors, aid in work efficiency improvement at a factory and form coaching in sports, for instance.
For estimation of a person's posture, it is desirable that the orientation of his/her trunk (i.e., the part from the shoulders to the waist) (which may be referred to as “body orientation” where appropriate) can be estimated. This is because the ability to estimate a person's body orientation would enable determination of the location of an object to which the person is paying attention or estimation of a direction in which the person is about to walk, for example.
It is desirable that such estimation can be performed without attaching an apparatus such as a orientation sensor on a person because an estimation technique requiring attachment of an apparatus on a person is difficult to apply to unspecified persons and is expensive when it targets many subjects.
To address these issues, a technique for estimating the body orientation of a person based on a video picture of the person is described in PTL 1, for example.
The technique described in PTL 1 (hereinafter referred to as “related art technique 1”) detects the shoulders and trunk of a person from captured video, analyzes the movement paths of the shoulders and trunk, and determines the person's body orientation from the analyzed movement path. This technique can estimate a person's body orientation without attaching an apparatus such as an orientation sensor on the person.
A technique for estimating the orientation of a person's face based on an image of the person is described in PTL 2, for example.
The technique described in PTL 2 (hereinafter referred to as “related art technique 2”) detects the face region of a person from a captured image and matches it against pre-learned patterns, thereby estimating the orientation of the person's face. With this technique, when the face is oriented to the front side of the body, that is, when the face orientation coincides with the body orientation, the body orientation can be estimated without attaching an apparatus such as an orientation sensor on the person.